Dubuque starts efforts to restore historic oak savanna
DUBUQUE, Iowa (AP) — For more than 3,000 years, the tri-state area was dominated by oak savannas.
The grand prairies of grasses, wildflowers, bushes and small flowering trees were dotted intermittently by great, sprawling oaks.
European colonizers quickly molded that landscape into the mosaic of agricultural, prairie, urban and close-canopied forest that dominates today. But the City of Dubuque has joined a regional movement toward the restoration of the historic oak savanna, hoping to glean the benefits that the unique landscape provides.
Dubuque has targeted swaths of Eagle Point Park and the Four Mounds site, which encompasses more than 220 acres, for these restorations. Both of them currently are in the design phase, the Telegraph Herald reported.
Restoring the oak savanna to Four Mounds complements the ongoing historic preservation of the site. But the return to the historic landscape also should better mitigate soil erosion and runoff than the manicured lawns and closed-canopy woods at both sites now.
Both sit atop bluffs, and both pour water and sediment off, which quickly finds its way into the Mississippi River.
“It’s a practice of keeping the water up on top before it can cause trouble,” said Jeff Ahlers, natural resources and sustainable practices specialist for the city’s parks division. “The best way to fix what is going on up there is to fix the habitat.”
Before European settlement, wildfire was a natural part of landscapes from the hardwood forests of New England to the desert Southwest. That includes southern Wisconsin, northern Illinois, all but the northwest corner of Iowa, and up into Minnesota where oak savannas dominated.
Oak savannas burned. They burned regularly. But their newest inhabitants didn’t like that.
“Fire has been a part of Iowa’s ecology since the glaciers retreated,” said Dale Maxson, a land steward at The Nature Conservancy’s Land of the Swamp White Oak Preserve west of Muscatine, Iowa. “When Europeans came to the area, they started putting out the natural grass fires as soon as they would start.”
And, as contrary as it might seem, fire was good for the plants.
“Historically, fire was a main thing,” Ahlers said. “Fire would go through the savanna, but oak is fire-resistant. The other tree species couldn’t take it as well.”
So, oaks were left alone, spreading their individual canopies wide over the hundreds of different plant species identified in the landscape’s understory, which grew back healthy after each burn.
Oak savannas historically had a canopy coverage of 5% to 30%, according to “A Potential Understory Flora for Oak Savanna in Iowa,” a 1996 article from The Journal of the Iowa Academy of Science by Karl Delong and Craig Hooper, of Grinnell College. Experts still use this catalog of species as the basis for oak savanna education today.
When Europeans began extinguishing those blazes, those other tree varieties — fed by the torrent of light allowed through the savanna’s open canopy — grew up quickly and began to compete with the oaks.
Any restoration project likely begins with removing the other varieties of trees, especially maples, that have grown up to outcompete the oaks.
“We have to protect the mature oaks,” Maxson said. “They grew up having full sunlight. We needed to reopen the canopy so those mature oaks can again have that. Oaks like open sunlight, they like coarse soils and they like fire.”
Oak savannas also were a great food source and regular grazing ground for species such as bison and deer. Europeans mimicked these animals’ activities by having livestock at Four Mounds for a time.
“This was lightly grazed until the Second World War,” said Jay Potter, conservation manager at Four Mounds. “Then, you can see in photos, it grew over the decades until it was remarkably dense.”
The resulting type of woodlands, seen at both Eagle Point and Four Mounds today, feature canopy coverage of 70% to 100%.
“When I look at a lot of Iowa’s woodlands, a lot of them are overstocked,” Maxson said. “There are too many trees per acre. It’s been so shaded out, just no native plants could thrive. Those grasses and wildflowers would have had a big impact on stabilizing soil.”
George and Viola Burden had what is now called the Historic Gray House built at Four Mounds in 1908. Folks can tour the mansion, a local landmark, to this day.
But the Burdens also enlisted Chicago landscape architect A. Phelps Wyman to design the grounds. He brought with him decorative plants of the time such as common buckthorn and oriental bittersweet.
The introduction of these invasive species, coupled with the increasingly infrequent occurrence of natural fire, caused problems. The buckthorn outcompeted much of the native groundcover now starved of light by the growing trees. A vine, the bittersweet, literally choked many of the oaks.
And, with no more fire, any invasives dropped by migrating birds grew up along with the trespassers.
Meanwhile, one year after the first house was built at Four Mounds, the city opened Eagle Point as a public park. That means manicured grass and lots of human activity and infrastructure.
“Lawns don’t soak up water,” Ahlers said. “All of these years of maintenance and people using the park, the soil is so hard that nothing seeps in.”
Four Mounds became a dense, closed-canopy woodland while Eagle Point became a traditional park.
Both lost the savanna’s unique ability to hold water in the soil and direct it downward.
The newest project at Four Mounds was made possible through a $200,000 state grant. But leaders there have been steering toward savanna restoration for years. They worked with the U.S. Fish and Wildlife Service to thin and cull invasives for a decade.
One area is nearing what an oak savanna would look like: Under the sprawling branches of a young burr oak, asters, black-eyed Susans, wild bergamot, big bluestem, many cereal grasses, St. John’s wort and more grow up to 3 feet tall.
The key to these landscapes’ success at soil retention, though, is that so much more of the plant grows in the opposite direction.
“As their roots grow down and they grow and die, grow and die, you’re getting more organic material in the soil,” Ahlers said.
While grasses make up most of an oak savanna, they need to be left alone to develop those roots.
“If they’re intending to manage it in a more wild setting, where the grasses and wildflowers are allowed to grow up farther, the roots are going to do the same thing,” Maxson said. “Beneath a lawn, the roots only go down a couple of inches. With a natural plant community, they have to be ready for drought cycles, so they shoot their roots way deep.”
University of Northern Iowa’s Tallgrass Prairie Center tours the Midwest with a banner that is 13 inches wide by 14 feet long.
Children lie on the ground beside it and marvel when it is unrolled at events. The banner is a life-sized portrait of a coupled big bluestem and leadplant root system — both regulars in the oak savanna.
That 14 feet of root depth compares to about 4 inches offered by a typical, manicured lawn grass.
And the prairie plants grow shoulder to shoulder on most of the ground not directly beneath an oak’s trunk. The coverage is fuller than that of a closed-canopy forest, where most of the ground beneath trees is covered with leaf debris rather than growing plants.
Dubuque is by no means the first community in the region to try an oak savanna restoration. Its predecessors have seen a range of benefits, including with erosion and runoff.
In 2004, a retired teacher named Don Hawkins approached Mineral Point (Wis.) School District officials with a plan to restore school property to the oak savanna.
Through his hard work and an eager workforce of faculty and students, two such savannas now exist.
One, next to Mineral Point High School, helped keep the land in place after its construction in the early 2000s.
“He took what was farmland and replaced it with its natural state,” said Don Hay, who began volunteering with Hawkins before essentially becoming his successor, with agriculture teacher Michael Robinson, after the original architect’s death. “The savanna there has clearly helped with erosion. I don’t know if that was part of the plan, but it has been a side benefit.”
Robinson said the Don Hawkins Oak Savanna at Mineral Point Elementary School has had the same effect.
“Having the vegetation we have seems to help in slowing those things down,” he said.
The benefits of returning these lands to their historical landscape don’t end with what is in the ground.
“When you look at biodiversity in Iowa, this is it,” Maxson said, from the Land of the Swamp White Oak. “This is where you’re going to see the greatest number of different species of plants and animals living and working together.”
In their seminal work, Delong and Hooper identified 252 species of understory plants in the historic oak savannas of Iowa. Those, plus the oaks themselves, are able to support a wide range of wildlife as well.
According to Iowa Department of Natural Resources forester Joe Herring, Iowa’s Wildlife Action Plan identifies 53 species of “great conservation need” that depend on oak savannas or similar habitats.
Eighteen birds, including the red-headed woodpecker, Baltimore oriole, barn owls, woodcocks and yellow-billed cuckoos, thrive in the oak savanna. Seventeen butterflies and 13 reptiles do as well. Of mammals, Elliot’s short-tailed shrew, the northern long-eared bat, Franklin’s ground squirrel and the spotted skunk benefit. Even an amphibian — Cope’s gray treefrog — can be expected.
That tapestry of life draws people as well, just as it did in the beginning. Hay said the Mineral Point schools have started to attract tourists interested in seeing the oak savannas and the rich biodiversity there.
“You might not think about it, but there are prairie people out there who come and just love it,” he said.
At Mineral Point, the savannas also serve as a learning opportunity.
“It’s been fantastic from the standpoint that it’s an awesome educational tool,” Hay said. “The Mineral Point community foundation has a fund specifically created for the oak savanna. The teachers apply for a grant, and they can do different projects.”
In the fall of 2018, elementary school students harvested seeds from the understory plants with the help of Robinson and his high school agriculture students. They spent the winter sprouting and caring for the plants.
On May 20, about 50 elementary students and their mentors returned to the savanna with their young sprouts to plant them. Those will help supplement the ecosystem already recovering there.
Any project of this scope comes with challenges, especially because the world is a different place than it was when savannas began to disappear.
“Our landscape is very changed from the past,” Maxson said.
Also, what benefits native species can benefit others.
“When we reopen the canopy, is that also going to favor undesirable species?” Maxson asked. “You need to be aware of that.”
Potter said that has proven true on areas of Four Mounds where restoration has been underway.
“If we don’t keep up with the work, it reverts back to a solid wall of brush,” he said.
And the native understory vegetation needs time to develop before it can face the fire that the savanna will need eventually.
“It is part of the city’s maintenance plan to burn,” Ahlers said. “But that’s three to five years after plants are first seeded. It’s long enough after for their presence to become established. Then those prairie plants can outcompete non-native plants.”
That will be Dubuque’s contracted consultants’ job over the next several months — devising a way to return the savanna to these sites without unintended consequences.
Eagle Point Park and Four Mounds are beloved places. There, generations of area families and visitors have picnicked, played, strolled, even lived, in the case of Four Mounds’ past. And at the end of this process, some of the manicured lawns at Eagle Point and the dense, shady woodlands at Four Mounds will be replaced by savanna.
The areas planned for restoration at Eagle Point, though, are currently more nuisance than nostalgic.
“We have areas we’ve been mowing that are steep at this point, nearly unsafe now to mow,” Ahlers said. “No one picnics there anymore. We won’t do anything that will take away from the way people use the park.”
Even so, Dubuque Park Division Manager Steve Fehsal acknowledged that there could be some grumbling from people who don’t want to see change.
The City of Dubuque has not yet contracted with a firm to complete the engineering on Eagle Point Park. But work at Four Mounds is set to begin this fall.
In Mineral Point, though, the savanna became so beloved it was the sticking point in a debate around possibly building a new elementary school elsewhere. The community saw the need, but doing so would move the students away from the savanna they helped restore. In the end, the vote was to instead renovate the school where it was.
“During the referendum, one of the reasons brought up to not move the school was its proximity to the oak savanna,” Hay said. “I think it made the difference. People are proud of it.”
Information from: Telegraph Herald, http://www.thonline.com